Reynolds-number scaling of wall-pressure--velocity correlations in wall-bounded turbulence
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| Format: | Preprint |
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2023
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| _version_ | 1866911752984199168 |
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| author | Baars, Woutijn J. Dacome, Giulio Lee, Myoungkyu |
| author_facet | Baars, Woutijn J. Dacome, Giulio Lee, Myoungkyu |
| contents | Wall-pressure fluctuations are a practically robust input for real-time control systems aimed at modifying wall-bounded turbulence. The scaling behaviour of the wall-pressure--velocity coupling requires investigation to properly design a controller with such input data so that it can actuate upon the desired turbulent structures. A comprehensive database from direct numerical simulations of turbulent channel flow is used for this purpose, spanning a Reynolds-number range $Re_τ\approx 550$-$5\,200$. Spectral analysis reveals that the streamwise velocity is most strongly coupled to the linear term of the wall-pressure, at a wall-scaling of $λ_x/y \approx 14$ (and $λ_x/y \approx 8.5$ for the wall-normal velocity). When extending the analysis to both homogeneous directions in $x$ and $y$, the peak-coherence is centred at $λ_x/λ_z \approx 2$ and $λ_x/λ_z \approx 1$ for $p_w$ and $u$, and $p_w$ and $v$, respectively. A stronger coherence is retrieved when the quadratic term of the wall-pressure is concerned, but there is only little evidence for a wall-attached-eddy type of scaling. Experimental data are explored in the second part of this work: wall-pressure data are denoised and subsequently used for predicting the binary-state of the streamwise velocity fluctuations in the logarithmic region. A binary estimation accuracy of up to 72% can be achieved by including both the linear and quadratic terms of the wall-pressure. This study demonstrates that a controller for wall-bounded turbulence (solely relying on wall-pressure data) has merit in terms of a sufficient state estimation capability, even in the presence of significant facility noise. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2307_06449 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Reynolds-number scaling of wall-pressure--velocity correlations in wall-bounded turbulence Baars, Woutijn J. Dacome, Giulio Lee, Myoungkyu Fluid Dynamics Wall-pressure fluctuations are a practically robust input for real-time control systems aimed at modifying wall-bounded turbulence. The scaling behaviour of the wall-pressure--velocity coupling requires investigation to properly design a controller with such input data so that it can actuate upon the desired turbulent structures. A comprehensive database from direct numerical simulations of turbulent channel flow is used for this purpose, spanning a Reynolds-number range $Re_τ\approx 550$-$5\,200$. Spectral analysis reveals that the streamwise velocity is most strongly coupled to the linear term of the wall-pressure, at a wall-scaling of $λ_x/y \approx 14$ (and $λ_x/y \approx 8.5$ for the wall-normal velocity). When extending the analysis to both homogeneous directions in $x$ and $y$, the peak-coherence is centred at $λ_x/λ_z \approx 2$ and $λ_x/λ_z \approx 1$ for $p_w$ and $u$, and $p_w$ and $v$, respectively. A stronger coherence is retrieved when the quadratic term of the wall-pressure is concerned, but there is only little evidence for a wall-attached-eddy type of scaling. Experimental data are explored in the second part of this work: wall-pressure data are denoised and subsequently used for predicting the binary-state of the streamwise velocity fluctuations in the logarithmic region. A binary estimation accuracy of up to 72% can be achieved by including both the linear and quadratic terms of the wall-pressure. This study demonstrates that a controller for wall-bounded turbulence (solely relying on wall-pressure data) has merit in terms of a sufficient state estimation capability, even in the presence of significant facility noise. |
| title | Reynolds-number scaling of wall-pressure--velocity correlations in wall-bounded turbulence |
| topic | Fluid Dynamics |
| url | https://arxiv.org/abs/2307.06449 |